Nichols



Jan. 31, 1956 A. NICHOLS 2,732,870

CAP FOR PLASTIC EXTRUSION TUBE CONTAINER Filed July 23, 1953 INVENTOR. Azvmom .MC'HOLS United States Patent CAP FOR PLASTIC EXTRUSION TUBE CONTAINER Anthony Nichole North Plainfield, N. J., assignor to Celluplastic Corporation, a corporation of New Jersey Application July 23, 1953, Serial No. 369,912

3' Claims. (Cl. 150.5)

This invention relates to an improved type of closure for plastic extrusion tube containers.

As is known, it is virtually impossible to manufacture plastic extrusion tubes with predetermined tube diameter and wall thickness. As a result considerable difficulty is experienced in getting a satisfactory seal with the standard type of unthreaded cap or plug closure which'is made to fit a certain size container of set dimensions.

In accordance with the present invention I provide a plug type cap for the container which is adapted to seal the mouth of the extrusion tube container by stretching the mouth of the tube a limited amount. The plug of the cap includes a lead in portion which is small enough to fit into the mouth of the tube regardless of variations in its diameter and which is connected to the plug by means of a connecting shank or taper which stretches the mouth of the container as the plug is pushed home in the tube. By stretching the mouth of the container around the plug I achieve a highly eflicient frictional seal between the mating surfaces of the plug and container. Excessive stretching of the mouth of the container to a point where it would give a loose fit is prevented by an annular flange spaced outwardly away from the plug which forms a slot surrounding the plug for receiving the mouth of the container.

My invention can be readily understood by reference to the accompanying drawing in which Fig. l is a front elevational view of my plug type cap for the plastic extrusion tube container shown.

Fig. 2 is a sectional view of the cap taken on line 2-2 of Fig. 1.

Fig. 3 shows an enlarged view of Fig. 2.

Referring to the drawings, container is an ordinary type of plastic extrusion tube which is sealed off at its bottom 12 to form the container shown. The container may be made of any suitable plastic material capable of extrusion molding such as the cellulose esters, cellulose ethers, or highly plasticized vinyl derivatives and the like. Preferably I use cellulose acetate or cellulose acetate butyrate for the extrusion tube. The manufacture of these extrusion tubes is well known in the art but with the equipment currently in use it is impossible as a practical matter to keep the diameter of the tube and its wall thickness constant. For example, with a tube one inch in diameter the thickness of the tube wall may vary about one thousandth of an inch or from approximately .013 to .012 inch and the outside diameter of the tube may vary about ten thousandths of an inch or from approximately 1.060 to 1.070 inch. With a tube of such variable dimensions, the ordinary type of cap which is made to fit a container of set dimensions does not give a satisfactory seal.

The cap I provide for such an extrusion tube container designated by 14 includes a top section 16 and a hollow thin walled plug or stem 18. Stem 18 includes a top portion 19 for sealing the mouth of the container and a lower lead in portion 20 for guiding the stem into "Fee .offset from top portion 19 and connected with it by means of aconnecting shank 22 which forms a taper between the lower lead in portion 20 and top sealing portion 19 of stem 18 for stretching the mouth of tube 10. Preferably the slope of connecting shank 22 is abrupt and its length should not exceed approximately 2 times the resulting increase in the diameter of lead in portion 20. That is, A should not exceed approximately 2 B.

The diameter of lead in portion 20 of stem 18 is made slightly smaller than the minimum inside diameter of extrusion tube 10 and the diameter of the top portion 19 of stem 18 is made slightly larger than the maximum inside diameter of tube 10. For example, if the extrusion tube has the dimensions described above I achieve a highly effective seal by making the diameter of lead in portion 20, approximately 1.025 inch and the .outside diameter of the 'top sealing portion 19 approximately 1.054 inch. With this construction the lead in portion 20 of cap 14 readily fits into the mouth of tube 10 and when the cap is pushed home connecting shank 22 stretches the ,mouth of the tube .as ,it rides up on stem 18. To avoid excessive stretching of the mouth of tube 10 to a point where it would fit loosely on top portion 19 of stem 18 I provide top section 16 with a flange 24 spaced outwardly from the stem which forms an annular slot 26 for seating and containing the open mouth of the tube. The lower end portion of flange 24 is preferably flared outwardly at 28 to assist in orienting the cap on the rim of container 10. For best results I make the mating portion of slot 26 approximately .031 inch deep so that a seal is achieved between surface areas of stem 18 and tube 10 and not just with the rim of tube 10. Since the width of annular slot 26 is made approximately .001 inch greater than thickness of the walls of extrusion tube 10, it readily receives tube 10 and guides the open mouth of the tube along the surface of the top portion 19 of stem 18. In addition flange 24 serves as a guard against excessive distortion of the mouth of the tube. For certain applications where an exceptionally tight seal is desired the width of slot 26 may be made approximately equal to the thickness of wall 10. When this is done slot 26 grips both the inside and outside surfaces at the mouth of tube 10 to materially increase sealing action of the cap.

The dimensions of cap 14 must be closely controlled to achieve the proper size relationship between the cap and extrusion tube. This may readily be done by forming cap 14 by means of any of the well known methods of molding such as by injection molding. Since the standard tolerance of a molded piece is plus or minus .005 thousandth, the maximum diameter of lead in portion 20 for the example given above would be 1.030 inch which is .004 thousandth less than the minimum inside diameter (1.034 inch) of extrusion tube 10. Similarly the minimum outside diameter of top portion 19 of stem 18 would be 1.049 inch which is .003 more than the maximum inside diameter (1.046 inch) of tube 10.

Since connecting shank 22 and stem 18 stretch the mouth of tube 10 the cap must have greater resistance to distortion than the tube. In general the cap may be made of any substantially rigid plastic material which is capable of being molded and which has greater resistance to distortion than the material of the tube. For example, when the cap is made by injection molding I may use polystyrene or one of the acetate materials or if the cap is made by compression molding I may use the phenolic or urea plastic materials. For best results I use a polystyrene cap for a tube of cellulose acetate and I prefer to keep the difference in hardness and resistance to distortion of the materials of the cap and enaasvo tube. equivalent to the diiference in hardness between P ysty ene. andcellulose acetate;

It will be understood that I do not intend to limit my invention to the example given herein which is merely chosen for the purpose; of illustration; Willi be further, understood thattit is intended to cover all changes and modifications of my'ittvention which: d'o'not" constitute departures from the spirit ancl'sco'pe oi? the invention. 7

What; I claimsisz. 7 i V V l. A,cap adapted: to: stretch. and; thereby seal; the

mouth of, an extrusion tube container of plastic. material, said cap comprising a:- thin, walled hollow stern, of substantially rigid plastic material which substantially conforms, to; the; shape oflthe, interior walls oi the tube in: the area around itstmoruth and which is capablect stretching; ,the,.mouth of. the container without distorting; the. st em,,v said; stem; havingi atop. sealing portion with outside diameter greater than the inside diameter of: the'container. in the area around:- the mouth: thereof and said; stem; having. it l'owenl'ead irr portion. ofiset from the toprsealingportion by means of ataper, said leadi i rr portion beingof smaller outside-- diameter than the insidediameter of the container so that'it' willreadily fit-thereinand said taper having an abrupt slope where in the length ofthe'taper'from top tobottom is not substantially' greater than two and one-half times the resulting' increase inthe diameter of the. said lead iii portion whereby the mouth of the tube is stretched as it rides. up over. the. taper to form a frictional. surface fitwith the top sealing portion of the stem when the cap is pushed home into the mouth of the container and said stem having a top covering section which extends outwardly over the rim of the container.

2. A structure as specified in claim 1 in which the top covering section of the stem also includes a thin walled annular flange spaced outwardly away from the stem to form'a sl'otaround' the top sealing portion of the stem for receiving the mouth of the container;

3. A structure as specified in claim 2 in which the width of the slot formed by said annular flange is approximately equal to the thickness ofthe wall of the container whereby the container wall? is tightly gripped on both its inside and outside surfaces by the top sealing portion of the stem and annular flange respectively when the container is pushed home into the slot.

References Cited in the file, of this patent UNITED STATES PATENTS 1,888,319 Hopkins NOV 22, 1932 2,127,268 Palmer Aug 16, 1938 2,329,375 Houlihan Sept. 14, 1943 2,364,216 'Hopwood Dec. 5, 1944 2,495,110 Kuhn Jan. 17, 1950 2,526,225 Gronemeyer et a1. Oct. 17, 1950 2,638,261 Poole May 12, 1953 

